I had a different experience. Our cars made almost exactly the same power. Mine came from the OEM update though.
My car LOVES the cold weather. To the point where I find the summer performance disappointing. In the winter, I could swear it has 40 WHP more! It's bitter sweet because of the decreased traction. :-/
2008 IB E92 M3| BBS | KW | Arkym | Platte Forme A.G. | Active Autowerke | K&N | Fabspeed | Dinan | Evolve-R